I better explain this more. I would like to make a two coloured soap. one colour on bottom, one on top. If I make my batter and lightly blend but not to trace then seperate into two batches if I stick blend the bottom layer but not the top batch will it thicken whilst I'm waiting for the bottom to set up? Hope that makes sense? Ta.
No, it shouldn't. I have used this technique several times, and unless you have a accelerating FO, your non-stick blended portion should remain more fluid that the bottom layer.
I would also divide up the fragrance oil and add not add it to the top layer until after you've poured the first. That's what I did with this one. Used the same fragrance in both layers, but scented the green layer and poured it, then added fragrance and did an ITP swirl for the top. Zappy soap rocks in the background.
In my experience, batter blended just to emulsion will continue to thicken, just at a slower rate than if blended to an obvious trace. But some recipes will thicken faster than others even if you stop mixing at emulsion. Temperature, the fatty acid profile, additives (especially fragrances) will also affect the working time.
Mix your batter to emulsion and then separate. Add your color and/or scent to Layer A and blend to a Medium Trace, pour, bounce and cover. So long as your batter is behaving, give the bottom layer 5 or 10 minutes and tidy up your work area. Then add color and/or scent to Layer B, and blend to a light trace. Uncover your mold and slowly pour Layer B in over your spatula to break the fall.